Photoelectrochemical production of Hydrogen Peroxide: A Computational Study from First Principles

Hydrogen peroxide (H₂O₂) is a highly effective oxidizing agent that sees wide use in industry. For example, it is employed in water treatment processes to remove organic impurities through the formation of highly reactive hydroxyl radicals. At present, H₂O₂ is mostly produced through the energy intensive anthraquinone process, and a greener alternative that requires less energy and makes use of non-toxic materials is highly desirable. Here we focus on the production of hydrogen peroxide directly by the photoelectrochemical splitting of water, through the two-electron water oxidation reaction (WOR). Several photoelectrodes have been used for the WOR and BiVO₄ has shown some promising properties, but it suffers from limited operational lifetimes. Based on the results of first principles calculations, we propose an alternative photoelectrode for the WOR, indium oxide (In₂O₃), which is chemically stable in water and commercially available. We carried out first principles molecular dynamics simulations of the In₂O₃/water interface with the SCAN functional and the Qbox code; we show that the valence and conduction bands of the hydroxylated (001) facet presents the desired alignment for the WOR. Importantly, such alignment is more favorable for the WOR than for the competing four electron oxygen evolution reaction. Work is in progress to further optimize the surface of In₂O₃ photoanodes via doping.